Conventionally, a disposable diaper as disclosed in Japanese Patent Publication (Laid-open) Toku-kai-hei 7-265357 is known. This disposable diaper is composed of a liquid-permeable top sheet 50, a leakage preventing back sheet 51, and an absorbent body 52 arranged between the both sheets 50 and 51, as shown in FIG. 80(A). The disposable diaper also serves as a pant-type of disposable diaper having a waist opening and a pair of leg openings formed by fastening both side portions of a front side and a back side together. In the both leg opening portions, elastic members 53, 53 . . . are continuously arranged along the peripheral edge. In a product state, as shown in FIG. 80(B), it is made into a pleat form by contraction of the elastic members 53, 53 . . . along the peripheral edges of the leg openings.
Also, a disposable diaper shown in FIG. 81(A) and FIG. 81(B) is disclosed in one of earlier development by the applicant (Japanese Patent Publication (Laid-open) Toku-kai 2001-178771). As shown in FIG. 81(A), the disposable diaper has: a paper diaper main body 63 including a structure which has a liquid-permeable top sheet 60 composed of mainly nonwoven fabric or the like, a waterproof film 61 composed of polyethylene or the like, and an absorbent body 62 such as a cottony pulp interposed between them; and an external sheet 64 integrally disposed on the outside of the diaper main body 63. The external sheet 64 comprises a back sheet nonwoven fabric 65 for an inner surface and a back sheet nonwoven fabric 66 for an external surface, which are laminated by a hot-melt adhesive. Elastic members 67 to 71 with various functions are interposed between the back sheet nonwoven fabric 65 and the back sheet nonwoven fabric 66, to be fastened by a hot-melt adhesive. Thereby the leakage of excretion is prevented and the property of fitting to the physique of a wearing person is improved.
Specifically, a plurality of elastic members 67 . . . , 68 . . . , e.g., a band rubber or the like, for around a waist are provided in the opening portions of front side section F and the opening of back side section B, respectively. A plurality of elastic members 69, 69 . . . are provided along lateral direction in the positions corresponding to the belly on a front side section F. In addition, a plurality of front side lifting elastic members 70, and 70 . . . composed of a thin rubber thread or the like are provided. Both ends of the elastic members 70 and 70 are located in the position corresponding to the belly on a front side section and the central portion of which is swelling downward to the under-the thigh portion. Also, a plurality of stretching elastic members for hip region 71 and 71 . . . are provided along the transverse direction at the hip region corresponding to the abdominal region of rear body B.
In such a pant-type of disposable diaper, as shown in FIG. 81(B), the stretching elastic members are not arranged along leg surrounding portions, therefore, pleat-form is not obtained as described above, but frills are formed along the leg surrounding portions.
However, in a pant-type of disposable diaper, as described above, when the frills are formed along the leg surrounding portions, the impression of prettiness is reinforced, but neat design is not obtained. And also the frills contact skin to cause itchiness to a wearing person, and further when wearing trousers thereon, the wearing person feels stiffening. This tendency is pointed out also by a questionnaire performed by this applicant recently. Conversely, it becomes clear that a disposable diaper presenting a neat appearance along the leg surrounding portions is preferred.
Also, in case of the disposable diapers, the ratio of crotch width to product width, and the ratio of side edge length to product length are large, therefore the impression of the crotch section becomes bulky, hardly presenting a neat appearance.
Moreover, pant-types of disposable diapers are constituted in such a way that both side edges of the front side section and the back side section of the external sheet are fastened to form a waist opening and a pair of right and left leg opening portions. In the center of the product width direction, a main absorptive body composed of an absorbent core interposed between a liquid-permeable top sheet and a leakage preventing back sheet is provided in a longitudinal direction extending from the front side section to the back side section. The pant-type of disposable diaper thus constituted is widely used.
Especially, in a belly side and a back side respectively, the pant-type of paper diaper has a plurality of stretching elastic members fastened with spaces in parallel along the peripheral direction of the body peripheral region ranging from the margins of the waist opening to the leg openings. The body peripheral region can be conceptionally divided into a waist section and an under waist section, and a plurality of elastic members are attached, respectively. The elastic members for waist and under-waist section certainly prevent the disposable diaper from slipping down. And especially the elastic members for under-waist section provide a product that is good in compatibility with the skin.
Further, there is also the so-called tape type disposable diaper, i.e., the type that fastens both right-and-left side edges on the belly side and both right-and-left side edges on the back side at the time of diaper use (at the time of wearing). This type of disposable diaper that includes no elastic members formed therein is widely used.
By the way, in the conventional paper diaper, edges of the leg openings in the crotch region that forms the leg openings is the remaining portion of the cut margin or a main absorptive body attachment margin in manufacture process, (henceforth a margin), having no stretchable members attached thereto, and formed of the material of the external sheet only (usually nonwoven fabric).
However, the edge of the leg openings serving as a margin is constituted in wave-like form and flatters, involving a problem of presenting bad appearance due to an unnecessary sense of volume body peripheral region.
On the other hand, it is considered that the problem is overcome by cutting the leg openings so that the margin may be lost. However, the margin may be unnecessary in a product state in manufacturing process, but it is required as cut margin or main absorptive body attachment margin. Therefore, it is not preferable to lose such a margin in view of manufacture.
Further, in the pant-type of disposable diaper currently used widely, a thin rubber thread is usually used as stretchable members arranged body peripheral region in recent years. The stretchable members are occasionally used for both of the waist opening section and under waist section, extending to a crotch section. In case of the under waist section, the stretchable member is made unevenly distributed in the waist opening side, not in the whole region of the under waist section. The arrangement space between the stretchable members is 10 mm or more. In addition, usually the arrangement space between the stretchable members in the waist opening section is small, whereas, the arrangement space between the stretchable members of the under waist section is made large, in order to prevent too much abdominal pressure.
On one hand, in order to prevent slipping down when wearing a product, diameter of each thin rubber thread is made large to enlarge shrink force.
On the other hand, in recent years, in order to give a soft feel, a nonwoven fabric sheet is arranged on the outside of the back side sheet made from plastic. This tendency is especially true of pant-type of paper diapers.
However, if the sheet that constitutes the external surface of a product is formed by a nonwoven fabric and a thin rubber thread is arranged to the use side of the nonwoven fabric, existence of the thin rubber threads is visible through the nonwoven fabric, due to the rough in-between structure of the nonwoven fabric. For a wearing person, the wearer's skin is rebuked by the thin rubber thread, and especially traces of rubber are possibly formed on the skin, resulting in the decline in consumer confidence.
Further, the nonwoven fabric has flexibility as compared with plastic sheets, such as polyethylene. Therefore, generation of wrinkles is remarkable in product external surface, and, further, indecent wrinkles occur. That is, in the stage of not wearing, as shown in FIG. 36(A), the wrinkles generated accompanying the stretching of the thin rubber threads G are generated with the form ranging from one side to another side of the adjoining thin rubber threads G. The uneven wrinkles generate repeatedly in the body peripheral direction. Furthermore, the adjoining wrinkles between thin rubber threads G and the next adjoining wrinkles thereto between thin rubber threads G do not continue, but are apt to generate independently.
When the arrangement space between mutual thin rubber threads is large, these wrinkles have long ridge or valley according to the separating distance of the mutual thin rubber threads, and the pitch of the unevenness in the body peripheral direction is large. Accordingly, if viewed on the whole in the external surface of a product, large wrinkles generate at random. The external surface of the product becomes stuffy, and the image is far from the pant-type of clothing.
Furthermore, each thin rubber thread G in the conventional product is thick, and its shrink force is large. Therefore, if one ridge wrinkle is taken for an embodiment, the valley on the thin rubber threads G side becomes deep, making the existence of the thin rubber thread G conspicuous. Further, since the ridge or the valley is large and shrink force acts strongly, complicated fine wrinkles generate at random in the ridge portion or the valley portion.
On the other hand, the existence of the thick rubber threads G is visible through the non-woven fabric. Therefore, it is feared that thick rubber threads G possibly bind a wearing person's skin tight strongly. Actually, in the side portion in which an absorbent body does not exist, the shrink force of the thick rubber threads G acts strongly, thereby forming traces of rubber. Further, friction of the inner surface of the product and the skin mainly in the portion where each rubber thread contact with the skin prevents the product from slipping down. However, since there are few rubber thread numbers per unit area, if very large shrinkage force does not work, the product may possibly slip down.
An object of the present invention is to provide a disposable diaper having a neat appearance of around leg openings, to overcome the above-described problem, and to provide a method for manufacturing the same.
Another object of the invention is to provide a disposable diaper having a neat appearance of crotch portion and around leg openings, to overcome the above-described problem.
A further object of the invention is to provide a disposable diaper with elastic members, existence of which is invisible or hardly visible, so as to make a wearing person undaunted by anxiety about excessive tightening and formation of traces of rubber, and provide a disposable diaper capable of solving the problem that the elastic members are visible, and appealing to consumers by high-class feeling of a product and good finish thereof.
A further object of the invention is to provide a disposable diaper excellent in appearance with no conspicuous wrinkles, having a neat appearance, that is, having no stuffy external surface with fine wrinkles even if wrinkles are generated, and presenting a flat face on the whole. And another object of the invention is to provide a disposable diaper with no formations of traces of rubber by being pressed to the skin on the face, avoiding too much pressure to the skin locally, and capable of improving the property of fitting to the physique of a wearing person by friction of the inner surface of the product and the skin on the whole surface, to thereby prevent the product from slipping down.
Another object of the invention is to provide a disposable diaper having leg opening edges hardly flutterable, having sufficient fitting property of leg surrounding portions, and good in appearance.